Omron E5ZN - Communications Errors

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Communications Errors Section 8-2
8-2 Communications Errors
Communications Not Possible or No Response
Probable cause Remedy
Communications
conditions
Baud rate of the E5ZN is different from that of the
host.
Set the same rate.
Communications method of the E5ZN is different
from that of the host.
Match the communications method of the E5ZN
to the host's communications conditions.
Connections Excessive number of E5ZN Units are connected
in parallel.
Do not connect an excessive number of E5ZN
Units.
• The number of E5ZN Units that can be con-
nected to the host for RS-485 communications
is 16 max.
Transmission path is too long. The transmission path must be within the permis-
sible range.
• The maximum RS-485 transmission path is
500 m in total.
Same unit number has been allocated more than
once on the same transmission path.
Make sure that different numbers are assigned to
all the E5ZNUnits that communicate with the host.
Communications data error due to ambient noise. • Move the communications cable away from the
source of noise.
• Use shielded communication cables.
• Use an Optical Interface.
• Write a program that makes it possible for the
host to detect a response error for any com-
mand that the host transmits and to re-transmit
it again.
Mistake in the use of the Optical Interface and
RS-232C/RS-485 Converter Units.
Refer to the datasheets of the Optical Interface
and RS-232C/RS-485 Converter Units used.
Terminators incorrectly attached to RS-485. Attach terminators only to the devices at each end
of the communications path.
Program System begins communications without any inter-
val after the E5ZN Units are turned ON.
Write a program so that the system starts commu-
nications with an interval of 4 s min. after the
E5ZN Units are turned ON.
Unstable signal of the E5ZN, which is generated
when the E5ZN is turned ON or OFF, is read as
data by the host.
Initialize the reception buffer of the host at the fol-
lowing stages.
• Before the host transmits the first command.
• After the E5ZN is turned OFF.
Host sends commands to the E5ZN before
receiving any response from the E5ZN.
Write a program enabling the host to read the
response after the host sends any command.
Interval between the time the host receives a
response and sends a command is too short.
The interval between the time the host receives a
response and sends a command must be 5 min-
utes minimum.
Program of the host is incorrect. • Correct the program.
• Check the command with the line monitoring
function.
• Run a sample program with the host.
Settings Unit numbers set with the selectors are different
from those set using the commands of the host.
The unit numbers must coincide.